Conventionally, crimp bonding, in which an electric wire is caulked and crimped by a terminal called open-barrel type, is common for connecting an electric wire and a terminal in a wire harness for motor vehicles. However, in such a wire harness, if moisture or the like attaches the connection part of the electric wire and the terminal, oxidization of metal surface that is used for the electric wire progresses, increasing the resistance at the joint part. Also, if different metals are used for the electric wire and the terminal, corrosion between different metals may progress. The progress of corrosion of metal materials at the connection part causes cracks or contact failure at the connection part and its effect on product life is unavoidable. Particularly in recent years, a wire harness having electrical wires made of aluminum alloy and terminals made of copper alloy has been in practical use, and the problem of corrosion at the joint part thereof has become noteworthy.
Here, if moisture attaches to the contacting part of different metals such as aluminum and copper for example, so-called electrolytic corrosion may occur due to difference in corrosion potential. Particularly, since the potential difference between aluminum and copper is large, corrosion on the side of aluminum, which is an electrically base metal, progresses. Therefore, the connection state between the conducting wires and crimp terminals becomes unstable, causing an increase in contact resistance or an enlargement of electrical resistance due to decrease in wire diameters, and, furthermore, disconnection of the wires may occur which may result in malfunction or breakdown of the electrical components.
Disclosed is such a wire harness in which different metals are in contact and resin material is filled to cover the connection part of electrical wires and crimp terminals (Patent Document 1). Filing the resin material prevents moisture from attaching to the contact part of electrical wires and crimp terminals.
Also, a method using a terminal having a cylindrical crimping portion of which one end is closed has been proposed (Patent Document 2). An end part of a coated wire is inserted into the cylindrical crimping portion, and then the cylindrical crimping portion is crimped by caulking to make the covered portion and the crimping portion adhered to each other so that moisture such as rain water or sea water can be prevented from entering into the inner core wire part of the crimping portion.